Since the beginning of the epidemic in 1981, 35 million people worldwide have died of HIV and AIDS. People now live long and reasonably healthy lives with HIV, thanks in large part to antiretroviral drugs that slow the growth of the virus.

Treatment is expensive, though, and is often associated with a wide range of side effects. Remaining free of HIV is still the best option. A number of lifestyle choices greatly increase the risk of contracting HIV. A few simple prevention strategies can almost completely eliminate the risk of HIV infection.

How is HIV spread?

HIV can’t spread through the air or through physical contact with an infected person. It can only be spread via a few bodily fluids. Those include:

Blood

Semen

Pre-seminal fluid

Rectal fluids

Vaginal fluids

Breast milk

HIV is considered a blood-borne illness, which means that the virus must come into contact with the blood to spread an infection. However, it is also spread through other bodily fluids as listed above. Exposure to infected fluids alone will not cause infection. For example, a person who touches infected blood will not become infected unless they have an open wound.

Fluid from a very small open wound on person with HIV can infect others. A person bitten by someone with HIV has a very small chance of contracting the virus if the biter has an open sore in their mouth.

Blood typically contains more of the virus than other bodily fluids, so exposure to infected blood is the riskiest of all HIV exposures. Blood injected directly into the bloodstream is more likely to cause an infection than blood that comes into contact with a small wound. This can happen in the form of needlestick injuries, intravenous drug use, or blood transfusions.

Unprotected vaginal and anal intercourse is the most common sources of HIV infections.

It’s a myth that HIV can be transmitted through:

Toilet seats

Swimming pools

Kissing

Water fountains

Tears

Physical contact with a person who has HIV

Pets

Risk factors for contracting HIV

Anyone can develop HIV, but a number of risk factors increase the risk. These include:

Frequent exposure to infected fluids, such as in medical or emergency settings.

Drug and alcohol use, which can undermine judgment. Between 2005-2009, 1 in 3 people infected with HIV in the United States used drugs or binged on alcohol.

Exposure to the virus during childbirth, pregnancy, or breastfeeding. Mothers and their babies can transmit the infection to one another.

Without any form of treatment in place, HIV transmission rates from mother to child range from 15-45 percent. Interventions such as antiretroviral treatment can reduce this rate to 5 percent.

A 2014 study looked at data on HIV transmission per 10,000 exposures to infected fluids. The number of infections for every 10,000 exposures was as follows:

Blood transfusion: 9,250

Sharing needles among injectable drug users: 63

Needlesticks (such as blood tests or vaccinations): 23

Being the receptive partner during anal intercourse: 138

Being the penetrative partner during anal intercourse: 11

Being the receptive partner during vaginal intercourse: 8

Being the penetrative partner during vaginal intercourse: 4

Today, the blood supply is safe. However, sharing needles among drug users remains a significant source of HIV transmission.

The Centers for Disease Control and Prevention (CDC) have a risk estimation tool on their website. It works out the risk of HIV transmission for different sexual activities where one person is HIV positive and the other is HIV negative. The tool is based on the most recent evidence.

Other methods of exposure, such as through oral sex, biting, and thrown bodily fluids produced a statistically non-existent risk of getting the virus. It’s possible to get HIV in these ways, but the risk is extremely small.

Because breast milk is so beneficial to babies, doctors continue to weigh the risks of breastfeeding-related HIV transmission.

A recent study that reviewed five previous studies on infected children giving their mothers HIV through breastfeeding found that the risk ranged between 40-60 percent. Open sores in the mouth can shed the virus into tiny sores on a mother’s breast. Mothers with HIV may also transmit the virus through breastfeeding.

The World Health Organization (WHO) recommends that women avoid breastfeeding when only one member of the mother-child pair has HIV and the mother is not taking antiretroviral drugs. However, there are different recommendations. Any decision to breastfeed should be an informed one that is made after speaking with a doctor.

Groups at highest risk of HIV

Some groups of people are more likely to develop HIV than others. This is due to a combination of lifestyle, economic, and health factors. This is not because HIV targets some groups more aggressively than others.

Groups at risk include:

Men who have sex with men: Anal intercourse is riskier than vaginal intercourse. Anti-homosexual stigma may also undermine men’s ability to access HIV services, or to confidently discuss safer sex.

Injectable drug users: Needle-sharing further increases the risk in this group. Around 13 percent of injectable drug users have HIV.

Sex workers: Stigma, power imbalances, and unsafe sex practices make sex workers vulnerable. Their risk of contracting HIV is 12 times higher than that of the general population.

Prisoners: Prisoners may engage in high-risk behaviour, such as needle-sharing and unsafe sex, which increases their exposure to HIV.

Children: Birth and breastfeeding are the most common means through which children contract HIV.

Teens and young adults: Young people are more likely than older adults to engage in high-risk behaviours, such as needle-sharing and unsafe sex.

Women: Receptive vaginal intercourse is more likely than penetrative vaginal intercourse to spread HIV. Gender inequality, including the threat of violence, may also reduce women’s ability to discuss safer sex.

Transgender people: Transgender people face discrimination and stigma, as well as violence. This can increase exposure to HIV and reduce negotiating power in relationships.

Reducing the risk of HIV

A range of strategies can reduce the risk of developing HIV. Steps that people can take include:

never sharing needles with another person

frequent HIV testing for anyone who has multiple sexual partners

avoiding breastfeeding when a woman or her child has HIV

using gloves and other sterile equipment in medical settings

practicing safer sex, including the use of condoms

Pregnant women with HIV should discuss risk mitigation strategies with their doctors.

People who already have HIV can reduce the risk of spreading the virus to someone else by taking antiretroviral drugs. These drugs also slow the spread of the virus, potentially prolonging life.

A 2016 study looked at couples in which one partner was HIV-positive. Even when the couples had intercourse without condoms, the HIV transmission rate over 3 years was zero when the HIV-positive partner took antiretrovirals. This does not mean that HIV drugs remove the risk entirely, but they do substantially reduce it.

Who should get tested for HIV?

Shortly after being infected with HIV, usually within a month, many people develop intense flu-like symptoms. People who experience these symptoms should see their doctor. However, not everyone develops these symptoms, so anyone who thinks they may have been exposed to HIV should see a doctor and get tested.

Frequent HIV testing is an inexpensive and effective way to stop the spread of HIV. Early diagnosis can also prolong life with prompt access to HIV drugs.

Testing in the following circumstances can slow the spread of HIV:

when planning to become pregnant, or after becoming pregnant

before having sex with a new partner

People who are at a high risk of contracting the virus, including sex workers, intravenous drug users, and those who regularly come into contact with bodily fluids, should get tested every 3-6 months.